System for filtering fluids

ABSTRACT

Disclosed is a system for filtering fluids comprising a primary filter ( 2 ) having at least one filter element that can be penetrated in one direction during the filtration process and can he penetrated in the opposite direction for a backflushing process, further comprising an aftertreatment device ( 36 ) which is mounted downstream of the priniaty filter ( 2 ) in order for the backflushed quantities discharged by the primary filter to be processed and which includes at least one filter chamber ( 11 ) that holds the backflushed quantities and has a fluid inlet, a fluid outlet and at least one aftertreatment filter element ( 19 ), and comprising a control device ( 9 ) for delivering one portion of the backflushed quantity at a time to the associated aftertreatment filter element ( 19 ).

The invention concerns a system for filtering fluids, comprising a primary filter that is provided with at least one filter element that allows flow-through in one direction during the filtration process, and allows flow-through in the opposite direction for a backflushing process, further comprising a post-treatment device, disposed downstream of the primary filter, for treating the backflushed volumes that are discharged by the primary filter.

To be able to provide a reliable and efficient operation of filtration plants over extended operating periods it is common, particularly with larger plants, to backflush and thus regenerate the filter elements used in the filtration process. During such backflushing phases, the filter element to be cleaned is subjected to a partial flow of the filtrate in the opposite direction so as to dislodge any contaminants from the element and to dispose of it together with the outflowing backflush volume. In view of the extreme environmental hazard of the contaminated backflushed fluid, the disposal thereof poses a problem. At least for larger volumes of flushing fluid, some post-treatment or processing is required, such as filtration of incinerabie contaminants. When filtering heavy fuel oils, such as those used to operate large diesels like marine diesel engines, the high viscosity of the heavy fuel oil hinders not only the backflushing process in the primary filter but also the filtration process, which must be carried out for processing by means of the post-treatment device, which is disposed downstream of the primary filter. In order to ensure an efficient backflushing action at the primary filter, even with fluids of higher viscosity, it is prior art according to the documents DE 10 2011 100 518 A1 or WO 2012/150011 A1 to use a certain quantity of flushing fluid from a piston accumulator for a respective backflushing process, wherein said piston accumulator is subjected to a media pressure so as to pass the backflush volume under pressure through the respective filter element to be backflushed to make it possible for dislodged contaminants to be flushed out even if the viscosity of the backflush fluid is high.

In view of the problems described above it is the object of the invention to provide a filtration system which not only ensures, also with fluids of higher viscosity, an efficient backflushing action at the primary filter but also effective treatment of the backflush volume discharged from the primary filter.

According to the invention, said object is met by a filtration system that exhibits the characteristics of claim 1 in its entirety.

Because the invention uses a control device for feeding the respective backflush volume in batches to an associated post-treatment filter element, it is possible to adapt the post-treatment filtration optimally to the characteristic of the backflush volume, such as viscosity and/or type of contamination, so that not only an effective backflush action can be achieved, but also a reliable treatment of the accruing backflush fluid.

In advantageous exemplary embodiments the control device comprises a control chamber with a first and a second fluid compartment, of which the first serves to receive the respective backflush volume and where a compressed gas, in particular in form of compressed air, is applied to the second fluid compartment at a predetermined working pressure. Thus the filter material of the respective post-treatment filter element allows flow-through by a backflush volume under a predetermined pressure. Depending on type and viscosity of the backflush fluid it is possible to adjust the working pressure in the second fluid compartment to a value that is optimal for a post-treatment filtration process, so that even in heavy oil applications, such as with marine diesel engines, the treated flushing oil that is obtained as filtrate is largely free of contaminants.

The first and the second fluid compartment of the control chamber are advantageously separated by a separating piston. Due to the separation the flushing oil is neither enriched by the working gas nor is it cooled down by the introduction of the gas. This ensures that a large part of the flushing oil, treated by the post-treatment device, can be returned to the unfiltrate side of the primary filter, which contributes to a reduction in fuel consumption of a respective ship. This also means that a smaller quantity of flushing oil is left over, which has to be collected in the ship and disposed of in port.

In advantageous exemplary embodiments a valve control system, in particular an electrically controlled 3/2-way valve, which has a compressed gas connection to the second fluid compartment of the control chamber, is provided for the supply and discharge of the compressed gas into and out of the second fluid compartment of the control chamber.

With the movement of the separating piston controlled in this manner, the first fluid compartment of the control chamber may have a permanent fluid connection with the unfiltrate side of the respective filter element within the filter chamber, wherein the filtrate side, which is separated from its unfiltrate side via the respective filter element, has at least sometimes a fluid connection with the fluid outlet.

In a particularly advantageous manner a further valve control device may be connected between the filtrate side of the respective filter element within the filter chamber and the fluid outlet into the respective fluid connection, in particular in form of a preferably spring-loaded non-return valve. This prevents the post-treatment device from running dry.

A further, third valve control device may be present with particular advantage on the side of the fluid inlet, which controls the intake of the respective backflush volume coming from the primary filter and into the post-treatment device. A motorised valve may be advantageously provided in this instance. If the post-treatment device is disposed downstream of a primary filter, as is disclosed in DE 10 2011 100 518 A1, the motorised valve, which in the description is referenced with the number 31 and which is arranged on the backflush volume outlet of said primary filter, can form the valve control device at the fluid inlet.

From a design point of view the post-treatment device may be made such that, seen in fluid flow direction, the control chamber is disposed upstream of the filter compartment with the respective filter element, or that the filter chamber with the respective filter element is disposed concentric to the control chamber and encloses the same.

With particular advantage the arrangement may be such that an energy store, preferably in form of a tension spring, is attached to the separating piston, and that the energy store passes through the second fluid compartment of the control chamber. To initiate a treatment filtration process, the separating piston may be moved by means of the tension spring in a direction that enlarges the volume of the first fluid compartment, so that a kind of suction effect is generated in the control chamber and in the filter chamber, and the control chamber is filled with a backflush volume that is released from the primary filter located upstream. After subsequent pressure application to the separating piston, the post-treatment filtration process can then take place at the predetermined, optimal pressure level.

In particularly advantageous exemplary embodiments, the post-treatment device is provided with a connector, which may be connected to the primary filter, wherein said connector is provided with a fluid inlet for backflushing volumes and a fluid outlet for post-treated backflushing volumes, wherein the connector acts as a support for the control chamber and for two of its associated filter chambers, which are disposed on either side of the control chamber in such a way that, within the connector, the first fluid compartment of the control chamber is permanently connected to the unfiltrate side of each of the filter chambers, and the filtrate sides of which are at least sometimes connected to the fluid outlet inside the connector. With a compact design that uses two filter chambers that can be operated together due to the control chamber being disposed between them, a particularly large, filter surface is available for an efficient treatment of even larger accruing backflush volumes.

In applications for fluids with a high viscosity, such as heavy oils, a heating device and/or an electronic pressure and/or temperature measuring device is preferably disposed at least in the fluid connection area between the control chamber and the filter chamber. Depending on temperature and viscosity of the backflush volume coming from the primary filter, a suitable temperature as well as the working pressure of the control chamber can be adjusted for the optimal filtration process.

With particular advantage, the post-treatment device may be connected to the primary filter such that the fluid quantity accrued at the fluid outlet of the post-treatment device may be recirculated to the unfiltrate side of the primary filter, thus forming a closed circuit. Said recirculation is particularly advantageous, especially with heavy oil marine applications, where it is a requirement that the flushing oil accrued during treatment is collected in the ship. Due recirculating a large part of accruing flushing oil, through which the fuel consumption of ships may be indirectly lowered, less flushing oil is left over, which eventually has to be disposed of in port.

According to claim 13 the object of the invention also concerns a post-treatment device for flushing oil, which is preferably a component of a filtration system that bears the characteristics of claims 1 to 12.

The invention will now be explained in more detail by way f exemplary embodiments shown in the drawing.

Shown are in:

FIG. 1 a perspective depiction, schematically simplified, of a partial vertical cross-section of an embodiment of the filtration system according to the invention;

FIG. 2 a perspective depiction of a quarter cross-section of the separately shown post-treatment device of the embodiment in FIG. 1;

FIG. 3 a central vertical cross-section of the post-treatment device of the embodiment in FIGS. 1 and 2;

FIG. 4 a vertical cross-section of the post-treatment device along line of FIG. 3;

FIG. 5 a slightly schematically simplified depiction of a longitudinal cross-section of the separately shown post-treatment device according to a second embodiment of the system according to the invention, wherein the starting state prior to the initiation of a treatment process is shown;

FIG. 6 a representation corresponding to FIG. 5, wherein the state at the beginning of a treatment process is shown;

FIG. 7 a representation corresponding to FIGS. 5 and 6, wherein the state during the treatment process is shown; and

FIG. 8 a schematically simplified longitudinal cross-section of a modified exemplary embodiment of the post-treatment device of the system according to the invention, wherein, as in FIG. 5, the state at the beginning of a treatment process is shown.

in the first embodiment of the system according to the invention, shown in FIGS. 1 to 4, the primary filter, the main housing of which is designated with the number 2 in FIG. 1, corresponds to the backflush filter device, which is described in the aforementioned document WO 20121150011 A1 and to which reference is made. Thus, the simplified representation of FIG. 1 does not show all details of this known device but only those details of said backflush filter device that are significant for understanding the system according to the invention, which as the primary filter is part of the system according to the invention. Nevertheless, it is self-evident that different types of backflush filter devices may be used as primary filters, for example the device disclosed in the already mentioned document DE 10 2011 100 518 A1.

Arranged on main housing 2, on which an inlet 8 for unfiltrate to be cleaned and an outlet 10 for cleaned fluid are located, are element chambers 4 on the outside, each of which contains one filter element (not visible in FIG. 1), which may be backflushed and which allows flow-through in a flow direction opposite to the normal filtration direction during a backflushing process. To generate a pneumatically supported backflush flow, a hydro-pneumatic piston accumulator 18 is provided in main housing 2, wherein the piston 20 of said piston accumulator separates a gas side 22 from a fluid side 24. FIG. 1 depicts the piston 20 in a position in which it is driven upwards through compressed air, where said compressed air is provided at the gas side 22 from a backflush gas tank filled with compressed air via membrane valve 14 and a backflush gas line 16. Due to this movement the piston 20 transferred the filtrate, previously located in fluid side 24, as pressurised backflush fluid via a backflush line 26 to a chamber connection (not shown) of a selected element chamber 4, the filter element of which is to be backflushed. The element chamber 4 that is to be backflushed is selected through setting the rotary position of the piston accumulator 18 by means of a rotary drive 6 that is assigned to it. The backflush volume with the dislodged contaminants exits from the clean-side chamber connection 28 from element chamber 4 and leaves the primary filter via a backflush outlet 32, from where it flows via a pipe connector 34 to the fluid inlet 3 of the associated post-treatment device 36.

The main body of the post-treatment device 36 is formed by a connector 1, which forms the support for two post-treatment filter chambers 11 as well as a control chamber 9, which forms the post-treatment control device, wherein said control chamber 9 is disposed in the central area of connector 1 between the two filter chambers 11 at the upper end of connector 1. Like the chamber housing 38 of the filter chambers 11, the control chamber 9 is flange-mounted on the upper cover wall 40 of connector 1 in such a way that control chamber 9 and chamber housing 38 of the filter chambers are open towards the inner hollow space located under the cover wall 40, wherein said hollow space forms a continuous passage 13 inside connector 1 between the filter chambers 11 and the control chamber 9. Flush with the longitudinal axis of control chamber 9, the fluid inlet 3 feeds into said passage 13, wherein said fluid inlet 3 is connected via the pipe connection 34 to the backflush outlet 32 of the primary filter. The pipe connection 34 contains a valve control device, for example in form of a spring-loaded non-return valve, which opens during the backflush process due to the pressure of the backflush volume, which is supplied by the piston accumulator 18. Alternatively, the pipe connection 34 may be provided with a motorised ball valve, for example the ball valve of the primary filter described in the cited document WO 20121150011 A1 where it is designated with the number 5.

As is clearly visible from FIG. 3, an internal pipe 42 extends in horizontal direction in the bottom section of the inner space of the connector 1 between the filter chambers 11. Located at both ends of the internal pipe 42 is an opening, the edge of which forms an element seat 46, on which a filter element 19, which is located in the associated filter chamber 11, is seated in such a way that the inner hollow filter space 17 of each filter element 19 is in fluid connection with the inner pipe 42. In the process of treatment filtration in which the filter material 21, which surrounds the inner hollow space 17, is subjected a flow from outside to the inside, the internal pipe 42 forms the filtrate side, from which the treated backflush volume flows to the fluid outlet 6, where a non-return valve 29 with a closing means 30 is disposed in order to prevent the system from running empty, said non-return valve may be slightly pre-tensioned into the closed position.

The control chamber 9, which is flange-mounted to the cover wall 40 of the connector 1, is formed by a circular cylinder that forms, in conjunction with a longitudinally moveable separating piston 43 inside said cylinder, a hydro-pneumatic piston accumulator, which is closed at the upper end by a lid 72. The separating piston 43 separates a first fluid compartment 51, which is connected to channel 13 inside the connector 1 and thus holds a backflush volume that flows in from the fluid inlet 3, from a second fluid compartment 53, which is provided for a pressure medium, in the present instance compressed air, that may be applied to the separating piston 43. Disposed on lid 72, which closes the second fluid compartment 43, is a valve control device 65 with which the pressure level in the second fluid compartment 53 of the control chamber 9 can be regulated, so that subsequent treatment filtrations take place in batches, each batch with a backflush volume that is provided by the control chamber 9 through the stroke movements of piston 43, wherein said stroke movements are generated by a working pressure that is present in a second fluid compartment 53.

The valve control device 65 is for this purpose provided with an electrically controllable 3/2-way valve 67, which has a connection 69 that leads to the second fluid compartment 53 of the control chamber 9. A second connection 71 leads, via an adjustable air regulator 73, to the flushing gas tank 12 (FIG. 1) of the primary filter, wherein said flushing gas tank serves as the source for compressed air. A pressure relief line 75, which leads to fluid outlet 5 and is connected to line 69, provides for pressure relief of the second fluid compartment 53.

The following operating sequence is achieved with this design:

In the starting state shown in FIGS. 1 to 4, in which the second fluid compartment 53 of the control chamber 9 is pressure-relieved via line 75, the backflush volume that flows into the first fluid compartment 51 from channel 13 has moved the piston 43 into the upper end position as shown. To initiate a treatment process, the valve 65 is switched into a position where compressed air flows in and applies pressure on the separating piston 43 so that it moves downwards; the backflush volume that is located in the first fluid compartment 51 is thus pushed out and flows via channel 13 and the open ends of the filter chambers 11 to the unfiltrate side 44, which is located between the outside of the filter material 21 of the filter elements 19 and the chamber wall 38 of the associated filter chamber 11. As a result of the unfiltrate pressure generated by the piston accumulator, the non-return valve disposed in pipe connection 34 has closed, or a possibly provided motorised valve was closed after completion of a backflush process of the primary filter. The treatment filtration process thus takes place under the filtration pressure generated by the working pressure in the second fluid compartment 53 of control chamber 9, wherein, with the non-return valve 29 open, the resulting filtrate flows away via the inner pipe 42 from the inner hollow space 17 of the filter elements 19 that form the filtrate side. As shown most clearly in FIG. 3, the chamber housings 38 of the filter chambers 11 have, in the direction of their closed upper end, a slightly conically reducing shape, so that the flow, cross-section of the unfiltrate side 44 is reduced from the lower inlet location towards the top, which, to provide a homogenous flow through the filter material 21, results in advantageous flow conditions.

The FIGS. 5 to 7 depict a post-treatment device 36 of a second embodiment of the system according to the invention. In this example the control chamber 9 is located at the top of connector 1 in the vicinity of the fluid inlet 3, and the only one filter chamber 11 is relocated on the connector 1 to the fluid outlet 5, which is located at the end of the connector 1 that is opposite the fluid inlet. Located upstream of fluid inlet 3 is a motorised valve 7, indicated in form of a symbol, which may be the motorised valve located at the backflush outlet 32 of the primary filter, which is designated with the reference number 53 in the mentioned document WO 2012/150011 A1 As with the first embodiment, in connector 1 a channel 13 follows on from the fluid inlet 3, which extends in the direction of the fluid outlet 5, but ends at a distance from it in the central part of the filter chamber 11 and forms at that end an inlet 15, which forms a fluid path into the inner hollow filter space 17 of the filter element 19 that is located in the filter chamber 11. The filter element 19, which surrounds the inner hollow space 17 with its filter material 21 that forms a hollow cylinder, is insertable and/or exchangeable via a removable housing lid 23 in the filter chamber 11.

The space 25, which forms the filtrate side in the treatment filtration process and which surrounds the filter material 21, is in connection with the fluid outlet 5 via a longitudinal channel 27, which extends in the area of the filter chamber 11 along the upper side of the connector 1, wherein the opening or closure of said connection can be facilitated via a further valve control device, which is implemented in the present example by a non-return valve 29. Said valve is spring-controlled and is provided with a closing means 30 that is pre-tensioned into a closed position shown in FIG. 5 by a closing spring 31, wherein the closing means 30 makes contact with a valve seat 33 and closes its opening. The non-return valve 29 is set to an approximate opening pressure of 0.5 bar, so that a corresponding, small pre-tension pressure remains in the fluid system to prevent it from running empty. To facilitate the filling process of the device, a vent hole 35 is provided in the housing lid 23 that ends in the hollow filter space 17 that forms the unfiltrate side, and a vent hole 37 is provided that ends in the filtrate space 25. The usual venting devices associated with the bore holes 35, 37 are not shown.

The main component of the control chamber 9 is a circular cylinder, which is flange-mounted with its lower end 41, when viewing the drawing, on the connector 1 in the vicinity of the fluid inlet 3 and is open to channel 13. The cylinder, together with the separating piston 43 that can move in it longitudinally, forms a hydro-pneumatic piston accumulator, which is closed at the upper end 45 of the cylinder by dome 47 that has a reduced diameter. The lower end of the dome 47 forms at the end 45 of the cylinder an end stop surface 49 to limit the movement of the separating piston 43 upwards, as shown in the drawing. Inside the cylinder and the dome 47, the separating piston 43 separates a first fluid compartment 51, which is connected to channel 13 and thus takes up the backflush volume that flows in from the fluid inlet 3, from a second fluid compartment 53, which is provided for a pressure medium, in this instance compressed air, with which to apply pressure to the separating piston 43. At the upper end the dome 47 is closed through a closing plate 55, at the inside of which an anchor 57 for a tension spring 59 is disposed, where the lower end of said spring is attached via an anchor 61 to the separating piston 43 and pre-tensioning it for a movement in which the volume of the first fluid compartment 51 is enlarged. A connection point 63 is disposed on the closing plate 55 for the valve control device 65, with which the pressure level in the second fluid compartment 53 of the control chamber 9 may be controlled in such a way that subsequent treatment filtrations take place in batches, each with a backflush volume, which is provided by the control chamber 9 in accordance with the stroke movements of the separating piston 43.

Like in the first embodiment, the valve control device 65 comprises an electrically controllable 3/2-way valve 67 from which a connecting line 69 leads to the connection point 63 at the control chamber 9. A second connecting line 71 leads via an adjustable air regulator 73 to a source for compressed air. A third connecting line 75 of valve 67 provides for pressure relief to the outside.

FIG. 5 depicts the starting state in which the channel 13 and the filter chamber 11 are filled with unfiltrate and are vented by means of bore holes 35 and 37. The second fluid compartment 53 is filled with compressed air via valve 67 so that pressure is applied to the separating piston 43 and is thus retained in the, lower position, as shown in FIG. 5, against the force of the extended tension spring 59. If backflushing is triggered in the upstream primary filter, the position of the 3/2-way valve 65 is changed, with the motorised valve 7 open, so as to discharge the compressed air from the second fluid compartment 53. The tension spring 59 now pulls the load-free separating piston 43 into the upper position, as shown in FIG. 6, so that a suction effect is created causing a backflush volume to flow in without opposing pressure via the fluid inlet 3, and when reaching the upper end position of the separating piston 43, see FIG. 6, the filter chamber 11 as well as the cylinder of the control chamber 9 are filled with backflush fluid. With the motorised valve 7 now closed, the valve 65 is switched into a position where compressed air flows in via the air regulator 73 and applies a load on separating piston 43 in such a way that it moves downward against the force of the tension spring 59. For the treatment filtration process, the, quantity of backflush fluid that remains in the cylinder of the control chamber 9 is pushed out as a result, as shown in FIG. 7, and is fed via channel 13 and the inlet 15 to the filter chamber 11. The filtrate obtained after flowing through the filter material 21 flows away from the filtrate compartment 25, which surrounds the filter element 19, to the longitudinal channel 27. Since the filtration process takes place under the filtration pressure that is generated by the working pressure in the second fluid compartment 53 of the control chamber 9, the non-return valve 29 opens the connection to the fluid outlet 5. The flow sequence that occurs during the filtration process is indicated in FIG. 7 with flow arrows.

As in the first embodiment, through adjusting the pressure level of the compressed air in the second fluid compartment 53 and through adjusting the movement speed of the separating piston 43 by means of the air regulator 73, the filtration pressure may be set for the optimal adaptation according to the nature and viscosity of the backflush fluid. For highly viscous fluids, such as heavy oil, it is possible to raise the temperature by means of a heating element 81 that is in heating contact with channel 13, wherein electrical power to the heating element 81 may be provided, or a supply of available process steam. To achieve optimal pressure and temperature settings it is possible to provide an electronic pressure and temperature sensor 83 that is in contact with the fluid in the channel 13.

The FIG. 8 depicts a modified exemplary embodiment in which the functionality is identical to that of the previously described exemplary embodiment. Thus the 3/2-way valve 67 at the connection point 63 of the dome 47 has been omitted in the drawing, as well as the non-return, valve 29 associated with the fluid outlet 5. The difference compared to the previous exemplary embodiment lies in the fact that the control chamber 9 is disposed coaxially inside the filter chamber 11. The latter comprises a circular cylinder 89, which is flange-mounted to connector 1, centrally between its fluid inlet 3 and fluid outlet 5. The inlet 15, which leads from channel 13 into the inner hollow filter space, forms on the outside of its raised rim 90 the element seat for the lower end of the filter element 19, the hollow cylinder-shaped filter material 21 of which separates the inner hollow space 17, which holds the unfiltrate, from the filtrate space 25, which is located between the outside of the filter material 21 and the cylinder 89. Like in the previous exemplary embodiment, the filtrate space 25 is connected, via a longitudinal channel 27 and an outlet opening 91 that is located thereon, to the fluid outlet 5. The cylinder 89 of the filter chamber 11 is closed at the upper end by a flange 92 of the cylinder of the control chamber 9. Extending away from flange 92, the cylinder extends to just before the raised rim 90 at the inlet 15, leaving a gap for the fluid connection to the space 17 that forms the unfiltrate side. As in the previous exemplary embodiment, a dome 47 forms again the upper end of the control chamber 9 as well as the end stop surface 49 as end stop for the separating piston 43. As before, the closing plate 55 of the dome 47 is provided with anchor 57 for the upper end of the tension spring 59 as well as the connection point 63 for the valve control device 65 comprising the 3/2-way valve 67. 

1. A system for filtering fluids, comprising a primary filter (2) that is provided with at least one filter element that allows flow-through in one direction during the filtration process, and allows flow-through in the opposite direction for a backflushing process, further comprising a post-treatment device (36), which is disposed downstream of the primary filter (2) for the treatment of the backflush volumes that are discharged from said primary filter, wherein said post-treatment device is provided with at least one filter chamber (11) that takes up the backflush volumes and is provided with a fluid inlet and a fluid outlet and with at least one post-treatment filter element (19), and a control device (9) for the batchwise supply of the respective backflush volume to the associated post-treatment filter element (19).
 2. The system according to claim 1, characterised in that the control device comprises a control chamber (9) with a first (51) and a second fluid compartment (53), of which the first (51) serves to receive the respective backflush volume and where a compressed gas, in particular in form of compressed air, is applied to the second fluid compartment (53) at a predetermined working pressure.
 3. The system according to claim 1, characterised in that the first (51) and the second fluid compartment (53) of the control chamber (9) are separated by a separating piston (43).
 4. The system according to claim 1, characterised in that a valve control system (65), in particular in form of an electrically controllable 3/2-way valve (67), which has a compressed gas connection to the second fluid compartment (53) of the control chamber (9), is provided for the supply and discharge of the compressed gas into and out of the second fluid compartment (53) of the control chamber (9).
 5. The system according to claim 1, characterised in that the first fluid compartment (51) of the control chamber (9) has a permanent fluid connection to the unfiltrate side (17; 44) of the respective filter element (19) within the filter chamber (11), and that the filtrate side (17; 25), which is separated via the respective filter element (19) from its unfiltrate side (17; 44), has at least sometimes a fluid connection to the fluid outlet (5).
 6. The system according to claim 1, characterised in that a further valve control device is connected between the filtrate side of the respective filter element (19) within the filter chamber (11) and the fluid outlet (5) into the respective fluid connection, in particular in form of a preferably spring-loaded non-return valve (29).
 7. The system according to claim 1, characterised in that a further third valve control device (7; 34) is present on the side of the fluid inlet (3), which controls the intake of the respective backflush volume coming from the primary filter (2) and into the post-treatment device (36).
 8. The system according to claim 1, characterised in that, seen in fluid flow direction, the control chamber (9) is disposed upstream of the filter chamber (11) with the respective filter element (19) or that the filter chamber (11) with the respective filter element (19) is disposed concentric to the control chamber (9) and encloses the same.
 9. The system according to claim 1, characterised in that an energy store, preferably in form of a tension spring (59), is attached to the separating piston (43), and that the energy store passes through the second fluid compartment (53) of the control chamber (9).
 10. The system according to claim 1, characterised in that the post-treatment device (36) is provided with a connector (1), which may be connected to the primary filter (2), wherein said connector is provided with a fluid inlet (3) for backflush volumes and a fluid outlet (5) for post-treated backflush volumes, wherein the connector acts as a support for the control chamber (11) and for two of its associated filter chambers (11), which are disposed on either side of the control chamber (9) in such a way that, within the connector (1), the first fluid compartment (51) of the control chamber (9) is permanently connected to the unfiltrate side (44) of each of the filter chambers (11), and the filtrate sides (17) of which are at least sometimes connected to the fluid outlet (5) inside the connector (1).
 11. The system according to claim 1, characterised in that a heating device (81) and/or an electronic pressure and/or temperature measuring device (83) is/are disposed at least in the fluid connection area (13) between the control chamber (9) and the respective filter chamber (11).
 12. The system according to claim 1, characterised in that the post-treatment device (36) is connected to the primary filter (2) such that the fluid quantity accrued at the fluid outlet (5) of the post-treatment device (36) may be recirculated to the unfiltrate side of the primary filter (2), thus forming a closed circuit.
 13. A post-treatment device, in particular as component of the system according to claim 1, comprising a connector (1) that may have a fluid connection with a primary filter (2) that releases backflush volumes of flushing oil and can be reverse-flushed, with at least one filter chamber (11) and at least one filter element (19) located at the connector (1), and a control device (9) for the batchwise supply of the respective backflush volumes to the associated filter element (19).
 14. The post-treatment device according to claim 13, characterised in that the control device comprises a control chamber (9) with a separating piston (43) that subdivides the control chamber (9) into a first (51) and a second fluid compartment (53), of which the first (51) serves to receive the respective backflush volume and where a compressed gas, in particular in form of compressed air, is applied to the second fluid compartment (53) at a predetermined working pressure. 